Net income was $1.9 billion for the quarter. For the full 2017 year, it was $3 billion. This was partly due to a tax cut that benefited Amazon to the tune of $789 million.

Jeff Bezos, founder and CEO, highlighted Alexa, the virtual assistant built into Amazon’s Echo devices, as a driver of the strong earnings. The Echo Dot and Amazon’s Fire TV Stick were its best-selling items in 2017. Echo alone was sold in the tens of millions, the company said.

“Our 2017 projections for Alexa were very optimistic, and we far exceeded them. We don’t see positive surprises of this magnitude very often – expect us to double down,” he said in a statement. “We’ve reached an important point where other companies and developers are accelerating adoption of Alexa.”

Amazon Web Services totaled $5.1 billion in sales, pretty much on par with the projected $5 billion earmark. AWS grew 45 percent year-over-year, compared with a 29 percent growth rate for North American sales and 45 percent for international. Physical stores, including Amazon bookstores and Whole Foods, raked in $4.5 billion in revenue.

For the full year, Amazon had $177.9 billion in sales, up 31 percent from the previous year’s $136 billion. Still, the company continued to invest in its business, resulting in a 2 percent drop in its operating profit to $4.1 billion.